1. Field of the Invention
The invention relates to automatically processing batches of postal items such as letters, large-format flat items or “flats” (e.g. magazines or newspapers in plastic or paper wrappers), or indeed parcels.
The invention relates more particularly to a method of processing postal items that consists in causing the postal items to advance in series past a camera for the purpose of generating an image of one face of each postal item, which face bears postal address information, in filtering the image of a current postal item for the purpose of isolating, in the image, at least one region of interest (ROI) containing the address information, and in sending the filtered image to an automatic recognition unit for automatically recognizing postal addresses by means of Optical Character Recognition (OCR) so as to extract the postal address from said filtered image and so as to direct the current postal item to a sorting outlet.
2. Discussion of the Background Art
OCR is a well-known image-processing technique in which images are recorded with suitable resolution and machine-recognizable symbols (in particular letters and numerals) are extracted from the images and are then evaluated. Modern OCR systems for automatically recognizing postal address information such as a postal delivery address can achieve processing throughputs of several tens of thousands of postal items per hour. However, the reliability of the recognition can vary considerably as a function of the writing style with which the address information is written on the postal items and also of the quantity of information appearing on the postal items. When the address information can be recognized automatically and unambiguously by OCR, the postal item corresponding to said address information can be directed automatically to a sorting outlet. Otherwise, the image of the postal item must be sent to a video coding system while the postal item itself waits to be sorted, which increases the processing costs for the postal operator.
Frequently, for a batch of postal items (for bulk mailing), the delivery addresses on the postal items are located at the same place on the face of each of the postal items, but that face also bears other address information such as the address of the sender of the postal item. In which case, automatic recognition cannot succeed because multiple addresses are present on the face of each of the postal items. It is possible to superpose a filter mask on the image generated for each postal item by the camera, in order to isolate one or more regions of interest (ROIs) in the image of the postal item, in which region(s) the relevant postal address information (in particular the postal delivery information) is situated, thereby contributing to reducing the recognition error rate.
After filtering, the image that is sent to the OCR automatic recognition unit is, for example, a blank (white-background) image (i.e. an image of the background of the mask) inside which appears, in a rectangle, only the delivery address block (i.e. a region of interest), e.g. in the form of gray-scale pixels of the original image generated by the camera. The filter mask can be more sophisticated in that it leaves visible, in gray scale, a plurality of distinct rectangular zones including postal address information. It is possible to provide ROI filtering that is different for different inlet lines of a sorting machine.
3. Description of the Related Art
Document U.S. Pat. No. 6,665,422 teaches using a video coding station for defining a region of interest. When a postal item image generated by the camera cannot be evaluated unambiguously by the OCR recognition unit, that image is displayed on the screen of a video coding station as superposed with a grid. The position in the image of the address block containing the address information is specified by the video coder which enters position data by using the grid, that position data then being delivered to the OCR recognition unit. That method of defining a region of interest can be implemented only for postal items processed in time-shifted manner.
Patent Document EP 0 596 724 also discloses a method of scanning a document containing a plurality of pages, that method consisting in reading a code on a separator placed at the beginning of the document. That code indicates the region to be scanned or “region of interest”. Unfortunately, Patent Document EP 0 596 724 does not make it possible to perform real-time automatic sorting or merely to update the region of interest.